Method and apparatus for transmitting and receiving control information to randomize inter-cell interference in a mobile communication system

ABSTRACT

A method and apparatus for transmitting and receiving control information in an SC-FDMA system are provided. Different orthogonal codes are generated for different slots each including a plurality of SC-FDMA symbols in a subframe. A control channel signal is generated by multiplying control symbols carrying control information by a sequence allocated for CDM of the control information. The control channel signal is multiplied by chips of the orthogonal codes on an SC-FDMA symbol basis and transmitted in the SC-FDMA symbols.

PRIORITY

This application claims priority under 35 U.S.C. §119(a) to a KoreanPatent Application filed in the Korean Intellectual Property Office onJan. 5, 2007 and assigned Serial No. 2007-1329, a Korean PatentApplication filed in the Korean Intellectual Property Office on Jan. 10,2007 and assigned Serial No. 2007-3039, and a Korean Patent Applicationfiled in the Korean Intellectual Property Office on May 10, 2007 andassigned Serial No. 2007-45577, the disclosures of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a mobile communicationsystem, and more particularly, to a method and apparatus fortransmitting and receiving control information to randomize inter-cellinterference caused by UpLink (UL) transmission in a future-generationmulti-cell mobile communication system.

2. Description of the Related Art

In the field of mobile communication technologies, Orthogonal FrequencyDivision Multiple Access (OFDMA), or Single Carrier-Frequency DivisionMultiple Access (SC-FDMA), has recently been studied for high-speedtransmission on radio channels. The asynchronous cellular mobilecommunication standardization organization, 3^(rd) GenerationPartnership Project (3GPP) is working on a future-generation mobilecommunication system, Long Term Evolution (LTE), in relation to themultiple access scheme.

The LTE system uses a different Transport Format (TP) for UL controlinformation depending on data transmission or non-data transmission.When data and control information are transmitted simultaneously on theUL, they are multiplexed by Time Division Multiplexing (TDM). If onlycontrol information is transmitted, a particular frequency band isallocated for the control information.

FIG. 1 is a diagram illustrating a transmission mechanism when onlycontrol information is transmitted on the UL in a conventional LTEsystem. The horizontal axis represents time and the vertical axisrepresents frequency. One subframe 102 is defined in time and aTransmission (TX) bandwidth 120 is defined in frequency.

Referring to FIG. 1, a basic UL time transmission unit, the subframe102, is 1 ms long and includes two slots 104 and 106, each 0.5 ms long.Each slot 104 or 106 is comprised of a plurality of Long Blocks (LBs)108 (or long SC-FDMA symbols) and Short Blocks (SBs) 110 (or shortSC-FDMA symbols). In the illustrated case of FIG. 1, a slot isconfigured so as to have six LBs 108 and two SBs 110.

A minimum frequency transmission unit is a frequency tone of an LB, anda basic resource allocation unit is a Resource Unit (RU). RUs 112 and114 each have a plurality of frequency tones. Herein, 12 frequency tonesform one RU, by way of example. Frequency diversity can also be achievedby forming an RU with scattered frequency tones, instead of successivefrequency tones.

Since the LBs 108 and the SBs 110 have the same sampling rate, the SBs110 have a frequency tone size twice that of the LBs 108. The number offrequency tones allocated to one RU in the SBs 110 is half that offrequency tones allocated to one RU in the LBs 108. In the illustratedcase of FIG. 1, the LBs 108 carry control information, while the SBs 110carry a pilot signal (or a Reference Signal (RS)). The pilot signal is apredetermined sequence by which a receiver performs channel estimationfor coherent demodulation.

If only control information is transmitted on the UL, it is transmittedin a predetermined frequency band in the LTE system. In FIG. 1, thefrequency band is at least one of the RUs 112 and 114 at either side ofthe TX bandwidth 120.

In general, the frequency band carrying control information is definedin units of RUs. When a plurality of RUs is required, successive RUs areused to satisfy a single carrier property. To increase frequencydiversity for one subframe, frequency hopping can occur, herein on aslot basis.

In FIG. 1, first control information (Control #1) is transmitted in theRU 112 in a first slot 104 and in the RU 114 in a second slot 106 byfrequency hopping. Meanwhile, second control information (Control #2) istransmitted in the RU 114 in the first slot 104 and in the RU 112 in thesecond slot 106 by frequency hopping.

The control information is, for example, feedback information indicatingsuccessful or failed reception of DownLink (DL) data,ACKnowledgment/Negative ACKnowledgment (ACK/NACK) that is generally 1bit. It is repeated in a plurality of LBs in order to increase receptionperformance and expand cell coverage. When 1-bit control information istransmitted from different users, Code Division Multiplexing (CDM) canbe considered for multiplexing the 1-bit control information. CDM ischaracterized by robustness against interference, compared to FrequencyDivision Multiplexing (FDM).

A Zadoff-Chu (ZC) sequence is discussed as a code sequence forCDM-multiplexing of control information. Due to its constant envelopmentin time and frequency, the ZC sequence offers good Peak-to-Average PowerRatio (PAPR) characteristics and excellent channel estimationperformance in frequency. PAPR is the most significant consideration forUL transmission. A higher PAPR leads to a smaller cell coverage, therebyincreasing a signal power requirement for a User Equipment (UE).Therefore, efforts should first be expanded toward PAPR reduction in ULtransmission.

A ZC sequence with good PAPR characteristics has a circularauto-correlation value of 0 with respect to a non-zero shift. Equation(1) below describes the ZC sequence mathematically.

$\begin{matrix}{{g_{p}(n)} = \left\{ \begin{matrix}{{\mathbb{e}}^{{- j}\frac{2\pi}{N}\frac{{pn}^{2}}{2}},} & {{when}\mspace{14mu} N\mspace{14mu}{is}\mspace{14mu}{even}} \\{{\mathbb{e}}^{{- j}\frac{2\pi}{N}\frac{{pn}{({n + 1})}}{2}},} & {{when}\mspace{14mu} N\mspace{14mu}{is}\mspace{14mu}{odd}}\end{matrix} \right.} & (1)\end{matrix}$where N denotes the length of the ZC sequence, p denotes the index ofthe ZC sequence, and n denotes the index of a sample of the ZC sequence(n=0, . . . , N−1). Because p and N should be relatively prime, thenumber of sequence indexes p varies with the sequence length N. Hencefor N=6, p=1,5, two ZC sequences are generated. If N is a prime number,N−1 sequences are generated.

Two ZC sequences with different p values generated by equation (1) havea complex cross-correlation, of which the absolute value is 1/√{squareroot over (N)} and the phase varies with p.

Control information from a user is distinguished from controlinformation from other users by a ZC sequence and is described ingreater detail by way of example.

Within the same cell, 1-bit control information from different UEs isidentified by time-domain cyclic shift values of a ZC sequence. Thecyclic shift values are UE-specific to satisfy the condition that theyare larger than the maximum transmission delay of a radio transmissionpath, thus ensuring mutual orthogonality among the UEs. Therefore, thenumber of UEs that can be accommodated for multiple access depends onthe length of the ZC sequence and the cyclic shift values. For example,if the ZC sequence is 12 samples long and a minimum cyclic shift valueensuring orthogonality between ZC sequences is 2 samples, multipleaccess is available to six UEs (=12/2).

FIG. 2 illustrates a transmission mechanism in which control informationfrom UEs is CDM-multiplexed.

Referring to FIG. 2, first and second UEs 204 and 206 (UE #1 and UE #2)use the same ZC sequence, ZC #1 in LBs, in a cell 202 (Cell A), andcyclically shift ZC #1 by 0 208 and Δ 210 respectively, for useridentification. In the illustrated case of FIG. 2, to expand cellcoverage, UE #1 and UE #2 each generate a control channel signal byrepeating the modulation symbol of intended 1-bit UL control informationsix times, i.e. in six LBs and multiplying the repeated symbols by thecyclically shifted ZC sequence, ZC #1 in each LB. These control channelsignals are kept orthogonal without interference between UE #1 and UE #2in view of the circular auto-correlation property of the ZC sequence.Δ210 is set to be larger than the maximum transmission delay of theradio transmission path. Two SBs in each slot carry pilots for coherentdemodulation of the control information. For illustrative purposes, onlyone slot of the control information is shown in FIG. 2.

In a cell 220 (Cell B), third and fourth UEs 222 and 224 (UE #3 and UE#4) use the same ZC sequence, ZC #2 in the LBs, and cyclically shift ZC#2 by 0 226 and Δ 228 respectively, for user identification. In view ofthe circular auto-correlation property of the ZC sequence, controlchannel signals from UE #3 and UE #4 are kept orthogonal withoutinterference between them.

This control information transmission scheme, however, causesinterference between different cells as control channel signals from UEsin the cells use different ZC sequences. In FIG. 2, UE #1 and UE #2 ofCell A use different ZC sequences from those of UE #3 and UE #4 of CellB. The cross-correlation property of the ZC sequences cause interferenceamong the UEs in proportion to the cross-correlation between the ZCsequences. Accordingly, there exists a need for a method for reducinginter-cell interference caused by control information transmission asdescribed above.

SUMMARY OF THE INVENTION

The present invention has been made to address at least the aboveproblems and/or disadvantages and to provide at least the advantagesdescribed below. Accordingly, an aspect of the present inventionprovides a method and apparatus for reducing inter-cell interferencewhen control information from different users is multiplexed in amulti-cell environment.

Another aspect of the present invention provides a method and apparatusfor further randomizing inter-cell interference by applying acell-specific or UE-specific random sequence to control information in asubframe.

A further aspect of the present invention provides a method andapparatus for notifying a UE of a random sequence applied to controlinformation in a subframe by Layer 1/Layer 2 (L1/L2) signaling.

An additional aspect of the present invention provides a method andapparatus for effectively receiving control information in a subframewithout inter-cell interference.

According to one aspect of the present invention, a method fortransmitting control information in an SC-FDMA system is provided.Different orthogonal codes are generated for different slots eachincluding a plurality of SC-FDMA symbols in a subframe. A controlchannel signal is generated by multiplying control symbols carryingcontrol information by a sequence allocated for CDM of the controlinformation. The control channel signal is multiplied by chips of theorthogonal codes on an SC-FDMA symbol basis and transmitted in theSC-FDMA symbols.

According to another aspect of the present invention, a method forreceiving control information in an SC-FDMA system is provided.Different orthogonal codes are generated for different slots eachincluding a plurality of SC-FDMA symbols in a subframe. A receivedcontrol channel signal is multiplied by a conjugate sequence of asequence allocated for CDM of the control information. The controlinformation is acquired by multiplying the multiplied control channelsignal by chips of the orthogonal codes on an SC-FDMA symbol basis.

According to a further aspect of the present invention, an apparatus fortransmitting control information in an SC-FDMA system is provided. Acontrol channel signal generator generates a control channel signal bymultiplying control symbols including control information by a sequenceallocated for CDM of the control information. A transmitter generatesdifferent orthogonal codes for different slots each including aplurality of SC-FDMA symbols in a subframe, multiplies the controlchannel signal by chips of the orthogonal codes on an SC-FDMA symbolbasis, and transmits the multiplied control channel signal in theSC-FDMA symbols.

According to an additional aspect of the present invention, an apparatusfor receiving control information in an SC-FDMA system is provided. Areceiver receives a control channel signal including controlinformation. A control channel signal receiver multiplies the controlchannel signal by a conjugate sequence of a sequence allocated for CDMof the control information and acquires the control information bymultiplying the multiplied control channel signal by chips of differentorthogonal codes used for different slots each including a plurality ofSC-FDMA symbols in a subframe, on an SC-FDMA symbol basis.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of certainexemplary embodiments of the present invention will be more apparentfrom the following detailed description when taken in conjunction withthe accompanying drawings, in which:

FIG. 1 is a diagram illustrating a transmission mechanism for controlinformation in a conventional LTE system;

FIG. 2 illustrates a transmission mechanism in which control informationfrom UEs is CDM-multiplexed;

FIG. 3 is a flowchart illustrating operation for transmitting controlinformation in a UE according to an embodiment of the present invention;

FIG. 4 is a flowchart illustrating operation for receiving controlinformation in a Node B according to an embodiment of the presentinvention;

FIG. 5 is a diagram illustrating a transmission mechanism for controlinformation according to an embodiment of the present invention;

FIGS. 6A and 6B are block diagrams illustrating a transmitter in the UEaccording to an embodiment of the present invention;

FIGS. 7A and 7B are block diagrams illustrating a receiver in the Node Baccording to an embodiment of the present invention;

FIG. 8 is a diagram illustrating a transmission mechanism for controlinformation according to an embodiment of the present invention;

FIG. 9 is a diagram illustrating another transmission mechanism forcontrol information according to an embodiment of the present invention;

FIGS. 10A and 10B are block diagrams illustrating a transmitter in theMS according to an embodiment of the present invention;

FIGS. 11A and 11B are block diagrams illustrating a receiver in the NodeB according to an embodiment of the present invention;

FIGS. 12A and 12B are diagrams illustrating a transmission mechanism forcontrol information according to an embodiment of the present invention;and

FIG. 13 is a diagram illustrating another transmission mechanism forcontrol information according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention are described in detailwith reference to the accompanying drawings. It should be noted thatsimilar components are designated by similar reference numerals althoughthey are illustrated in different drawings. Detailed descriptions ofconstructions or processes known in the art may be omitted to avoidobscuring the present invention.

Embodiments of the present invention provide transmission and receptionoperations of a UE and a Node B in the case where UL control informationfrom a plurality of UEs are multiplexed over a predetermined frequencyarea of a system frequency band.

Embodiments of the present invention will be described in the context ofCDM transmission of control information from a plurality of UEs in anSC-FDMA cellular communication system. Embodiments of the presentinvention are also applicable to multiplexing that does not shareparticular time-frequency resources, for example, FDM or TDMtransmission of the control information. CDM can be one of various CDMAschemes including time-domain CDMA and frequency-domain CDM.

For CDM, a ZC sequence is used, although any other code sequence withsimilar characteristics is also available for use. The controlinformation is 1-bit control information such as ACK/NACK herein, by wayof example. However, an inter-cell interference reduction method of thepresent invention is also applicable to control information with aplurality of bits such as a Channel Quality Indicator (CQI). In thiscase, each bit of the control information is transmitted in one SC-FDMAsymbol. The inter-cell interference reduction method is also applicableto CDM transmission of different types of control information, forexample, 1-bit control information and control information with aplurality of bits.

Inter-cell interference occurs when UEs in adjacent cells transmit theircontrol information using different ZC sequences of length N in MSC-FDMA symbols, i.e. M LBs being UL time transmission units.

If the phases of the correlations between sequences in LBs from UEswithin adjacent cells are randomized while the circular auto-correlationand cross-correlation properties of the ZC sequence are maintained, thephase of interference between the adjacent cells is randomized acrossthe LBs during accumulation of the LBs carrying the control informationfor a subframe at a receiver, thus decreasing an average interferencepower.

In accordance with an embodiment of the present invention, each UEgenerates its ZC sequence on an LB basis in a subframe and applies arandom sequence having a random phase or a random cyclic shift value tothe ZC sequence in each LB, thereby randomizing the ZC sequence. Thenthe UE transmits control information by the randomized ZC sequence. Therandom sequence is cell-specific. The interference randomization isfurther increased using a different random sequence of phase values orcyclic shift values for each UE.

The embodiments of present invention propose three methods. In thefollowing description, a ZC sequence of length N is denoted by g_(p)(n).The ZC sequence g_(p)(n) is randomized over M LBs and controlinformation is multiplied by the randomized ZC sequence g′_(p,m,k)(n)where k denotes the index of a channel carrying the control information.

Equation (2) describes the randomized ZC sequence according to Method 1.g′ _(p,m,k)(n)=g _(p)((n+d _(k))mod N)·S _(M,m),  (2)(m=1,2, . . . ,M, n=0,1,2, . . . ,N−1)where d_(k) denotes a cyclic shift value of the same ZC sequence, bywhich channel k carrying the control information is identified. Thecyclic shift value is preferably a time-domain cyclic shift valuealthough it can be a frequency-domain cyclic shift value. In equation(2), mod represents modulo operation. For instance, A mod B representsthe remainder of dividing A by B.

S_(M,m) denotes an orthogonal code of length M, being +1s or −1s. Thisorthogonal code can be a Walsh code. m denotes the index of an LB towhich the control information is mapped. If the control information isrepeated four times in the slots of a subframe, the chips of a Walshsequence of length 4 are multiplied one to one by the LBs of each slot,and a combination of Walsh sequences for two slots in the subframe isdifferent for each cell, thus randomizing inter-cell interference. Foradditional randomization, a different combination of Walsh sequences canbe used for each UE.

Equation (3) describes the randomized ZC sequence according to Method 2.g′ _(p,m,k)(n)=g _(p)((n+d _(k))mod N)·e ^(jφ) _(m) ,  (3)(m=1,2, . . . ,M, n=0,1,2, . . . ,N−1)where φ_(m) denotes a random phase value that changes the phase of theZC sequence g_(p)(n) in each LB. Inter-cell interference is randomizedby using different sets of random phase values, i.e. different randomphase sequences {φ_(m)} for adjacent cells in LBs of a subframe.

Equation (4) describes the randomized ZC sequence according to Method 3.g′ _(p,m,k)(n)=g _(p)((n+d _(k)+Δ_(m))mod N),  (4)(m=1,2, . . . ,M, n=0,1,2, . . . ,N−1)where Δ_(m) denotes a random cyclic shift value that changes thetime-domain cyclic shift value d_(k) of the ZC sequence g_(p)(n) in eachLB. Inter-cell interference is randomized by using different sets ofrandom time-domain cyclic shift values, i.e. different randomtime-domain cyclic shift sequences {Δ_(m)} for adjacent cells in LBs ofin a subframe. While the random cyclic shift values are used in the timedomain herein, they can be adapted to be used in the frequency domain.

FIG. 3 is a flowchart illustrating an operation for transmitting controlinformation using a randomized ZC sequence according to an embodiment ofthe present invention.

Referring to FIG. 3, a UE receives sequence information and randomsequence information from a Node B by signaling in step 302. Thesequence information is about a ZC sequence for use in transmittingcontrol information, including the index of the ZC sequence and a cyclicshift value. The random sequence information is used for randomizing theZC sequence, including a random phase sequence being a set of randomphase values or a random time-domain cyclic shift sequence being a setof random time-domain cyclic shift values, for application to LBs of asubframe. The signaling is upper-layer (e.g. L2) signaling or physicallayer (L1) signaling. To randomize inter-cell interference, the randomphase sequence or the random time-domain cyclic shift sequence isdifferent for each cell. For further interference randomization, therandom phase sequence or the random time-domain cyclic shift sequencecan also be set to be different for each UE.

In step 304, the UE generates control information and generatescomplex-valued modulation symbols (hereinafter, referred to as controlsymbols) using the control information. The number of the controlsymbols is equal to that of LBs allocated for transmission of thecontrol information. For example, if the control information is 1 bit,the UE creates as many control symbols as the number of the allocatedLBs by repetition.

In step 306, the UE generates the ZC sequence using the index and thecyclic shift value included in the sequence information. The UE thengenerates random values according to the random phase sequence or therandom time-domain cyclic shift sequence included in the random sequenceinformation in step 308. The random values are a Walsh sequence, randomphase values, or random time-domain cyclic shift values. These randomvalues are different for each cell and/or each UE. The UE generates arandomized ZC sequence by applying the random values to the ZC sequenceon an LB basis in step 310. In step 312, the UE multiplies therandomized ZC sequence by the control symbols, maps the products to theLBs, and transmits the mapped LBs.

FIG. 4 is a flowchart illustrating an operation for receiving controlinformation in the Node B according to an embodiment of the presentinvention.

Referring to FIG. 4, the Node B acquires a correlation signal bycorrelating a signal received from an intended UE in a plurality of LBswith a ZC sequence applied to the signal in step 402. In step 404, theNode B performs channel estimation on a pilot signal received from theUE and performs channel compensation for the correlation signal usingthe channel estimate. The Node B acquires control information byapplying random values corresponding to the UE to thechannel-compensated correlation signal on an LB basis and thus removingrandom values from the channel-compensated correlation signal in step406. The random values corresponding to the UE are known from randomsequence information that the Node B transmitted to the UE.

In the above transmission and reception of control information, an LB(i.e. an SC-FDMA symbol) is a basic unit to which the controlinformation is mapped for transmission. The ZC sequence is repeated inunits of LBs and the elements of the random phase sequence or the randomtime-domain cyclic shift sequence change LB by LB.

In the case where a plurality of cells exist under the same Node B, UEswithin each cell multiplex their control channels using the same ZCsequence and different time-domain cyclic shift values. If differentrandom phase sequences or random time-domain cyclic shift sequences areused on an LB basis in the cells of the Node B, orthogonality may belost among UEs. Under this environment, therefore, a random phasesequence or a random time-domain cyclic shift sequence is specific tothe Node B and the cells of the Node B use the same random sequence.

A first embodiment of the present invention implements Method 1described in equation (2).

FIG. 5 illustrates a transmission mechanism for control informationaccording to the first embodiment of the present invention.

Referring to FIG. 5, the same 1-bit control information occurs 8 timesin one subframe and is subject to frequency hopping on a slot basis inorder to achieve frequency diversity. If two SBs and the first and lastLBs carry pilots for channel estimation in each slot, the remaining LBsof the slot can be used for transmitting the control information. Whileone RU is used for transmitting the control information herein, aplurality of RUs can be used to support a plurality of users.

In a first slot, modulation symbols carrying the 1-bit controlinformation occur four times, for transmission in four LBs and aremultiplied by an orthogonal code of length 4, S1 502 (=S1 _(4,1) S1_(4,2) S1 _(4,3) S1 _(4,4)) on an LB basis. S1 _(4,x) represents chip xof the orthogonal code S1. The pilot sequence is also multiplied by anorthogonal code of length 4, S1′ 504 (=S1′_(4,1) S1′_(4,2) S1′_(4,3)S1′_(4,4)) on an LB or SB basis. The use of orthogonal codes canincrease the number of multiple-access users. For example, for length 4,four orthogonal codes are available. The use of the four orthogonalcodes enable four times more users to be accommodated in the sametime-frequency resources, as compared to non-use of orthogonal codes.

In a second slot, the 1-bit control information occur four times and ismultiplied by an orthogonal code of length 4, S2 506 (=S2 _(4,1) S2_(4,2) S2 _(4,3) S2 _(4,4)) on an LB basis. The pilot sequence is alsomultiplied by an orthogonal code of length 4, S2′ 508 (=S2′_(4,1)S2′_(4,2) S2′_(4,3) S2′_(4,4)) on an LB or SB basis.

The Node B signals the orthogonal codes S1 502, S1′ 504, S2 506, and S2′508 to the UE. Due to the nature of the orthogonal codes, their lengthsshould be multiples of 4. In FIG. 5, orthogonal codes of length 4 areapplied to each slot. If frequency hopping does not take place on a slotbasis in the transmission mechanism of FIG. 5, it can be considered thatthe control information experiences a negligibly small channel change infrequency during one-subframe transmission. Therefore, orthogonality isstill maintained even though the length of the orthogonal codes isextended to one subframe. In this case, orthogonal codes of length 8 canbe used for transmitting the control information in one subframe.

A different combination of orthogonal codes to be applied to the slotsof one subframe is set for each cell to randomize inter-cellinterference. For example, for transmitting control information in theslots, Cell A uses orthogonal codes {S1,S2} sequentially and Cell B usesorthogonal codes {S3,S4} sequentially. The orthogonal code combination{S3,S4} includes at least one different orthogonal code from theorthogonal code combination {S1,S2}.

FIGS. 6A and 6B are block diagrams illustrating a transmitter in the UEaccording to an exemplary embodiment of the present invention.

Referring to FIG. 6A, the transmitter includes a controller 610, a pilotgenerator 612, a control channel signal generator 614, a data generator616, a Multiplexer (MUX) 617, a Serial-to-Parallel (S/P) converter 618,a Fast Fourier Transform (FFT) processor 619, a mapper 620, an InverseFast Fourier Transform (IFFT) 622, a Parallel-to-Serial (P/S) converter624, an orthogonal code generator 626, a multiplier 628, a Cyclic Prefix(CP) adder 630, and an antenna 632. Components and an operation relatedto UL data transmission will not be described herein.

The controller 610 provides overall control to the operation of thetransmitter and generates control signals required for the MUX 617, theFFT processor 619, the mapper 620, the pilot generator 612, the controlchannel signal generator 614, the data generator 616, and the orthogonalcode generator 626. The control signal provided to the pilot generator612 indicates a sequence index and a time-domain cyclic shift value bywhich to generate a pilot sequence. Control signals associated with ULcontrol information and data transmission are provided to the controlchannel signal generator 614 and the data generator 616.

The MUX 617 multiplexes a pilot signal, a data signal, and a controlchannel signal received from the pilot generator 612, the data generator616, and the control channel signal generator 614 according to timinginformation indicated by a control signal received from the controller610, for transmission in an LB or an SB. The mapper 620 maps themultiplexed signal to frequency resources according to LB/SB timinginformation and frequency allocation information received from thecontroller 610.

When only control information is transmitted without data, theorthogonal code generator 626 generates orthogonal codes for LBs/SBsaccording to information about cell-specific or UE-specific orthogonalcodes to be used for slots, received from the controller 610, andapplies the chips of the orthogonal codes to the control symbols of thecontrol channel signal mapped to LBs according to timing informationreceived from the controller 610. The orthogonal code information isprovided to the controller 610 by Node B signaling.

The S/P converter 618 converts the multiplexed signal from the MUX 617to parallel signals and provides them to the FFT processor 619. Theinput/output size of the FFT processor 619 varies according to a controlsignal received from the controller 610. The mapper 620 maps FFT signalsfrom the FFT processor 619 to frequency resources. The IFFT processor622 converts the mapped frequency signals to time signals and the P/Sconverter 624 serializes the time signals. The multiplier 628 multipliesthe serial time signal by the orthogonal codes generated from theorthogonal code generator 626. That is, the orthogonal code generator626 generates orthogonal codes to be applied to the slots of a subframethat will carry the control information according to the timinginformation received from the controller 610.

The CP adder 630 adds a CP to the signal received from the multiplier628 to avoid inter-symbol interference and transmits the CP-added signalthrough the transmit antenna 632.

FIG. 6B is a detailed block diagram illustrating the control channelsignal generator 614 according to an embodiment of the presentinvention.

Referring to FIG. 6B, a sequence generator 642 of the control channelsignal generator 614 generates a code sequence, for example, a ZCsequence on an LB basis. To do so, the sequence generator 642 receivessequence information such as a sequence length and a sequence index fromthe controller 610. The sequence information is known to both the Node Band the UE.

A control information generator 640 generates a modulation symbol having1-bit control information, and a repeater 643 repeats the control symbolto produce as many control symbols as the number of LBs allocated to thecontrol information. A multiplier 646 CDM-multiplexes the controlsymbols by multiplying the control symbols by the ZC sequence on an LBbasis, thus producing a control channel signal.

The multiplier 646 functions to generate the user-multiplexed controlchannel signal by multiplying the symbols output from the repeater 643by the ZC sequence. A modified embodiment of the present invention canbe contemplated by replacing the multiplier 646 with an equivalentdevice.

FIGS. 7A and 7B are block diagrams illustrating a receiver in the Node Baccording to an embodiment of the present invention.

Referring to FIG. 7A, the receiver includes an antenna 710, a CP remover712, an S/P converter 714, an FFT processor 716, a demapper 718, an IFFTprocessor 720, a P/S converter 722, a Demultiplexer (DEMUX) 724, acontroller 726, a control channel signal receiver 728, a channelestimator 730, and a data demodulator and decoder 732. Components and anoperation associated with UL data reception will not be describedherein.

The controller 726 provides overall control to the operation of thereceiver, and generates control signals required for the DEMUX 724, theIFFT processor 720, the demapper 718, the control channel signalreceiver 728, the channel estimator 730, and the data demodulator anddecoder 732. Control signals related to UL control information and dataare provided to the control channel signal receiver 728 and the datademodulator and decoder 732. A control channel signal indicating asequence index and a time-domain cyclic shift value is provided to thechannel estimator 730. The sequence index and the time-domain cyclicshift value are used to generate a pilot sequence allocated to the UE.

The DEMUX 724 demultiplexes a signal received from the P/S converter 722into a control channel signal, a data signal, and a pilot signalaccording to timing information received from the controller 726. Thedemapper 718 extracts those signals from frequency resources accordingto LB/SB timing information and frequency allocation informationreceived from the controller 726.

Upon receipt of a signal including control information from the UEthrough the antenna 710, the CP remover 712 removes a CP from thereceived signal. The S/P converter 714 converts the CP-free signal toparallel signals and the FFT processor 716 processes the parallelsignals by FFT. After demapping in the demapper 718, the FFT signals areconverted to time signals in the IFFT processor 720. The input/outputsize of the IFFT processor 720 varies according to a control signalreceived form the controller 726. The P/S converter 722 serializes theIFFT signals and the DEMUX 724 demultiplexes the serial signal into thecontrol channel signal, the pilot signal, and the data signal.

The channel estimator 730 acquires a channel estimate from the pilotsignal received from the DEMUX 724. The control channel signal receiver728 channel-compensates the control channel signal received from theDEMUX 724 by the channel estimate and acquires control informationtransmitted by the UE. The data demodulator and decoder 732channel-compensates the data signal received from the DEMUX 724 by thechannel estimate and then acquires data transmitted by the UE based onthe control information.

When only control information is transmitted without data on the UL, thecontrol channel signal receiver 728 acquires the control information inthe manner described with reference to FIG. 5.

FIG. 7B is a detailed block diagram illustrating the control channelsignal receiver 728 according to an embodiment of the present invention.

Referring to FIG. 7B, the control channel signal receiver 728 includes acorrelator 740 and a derandomizer 742. A sequence generator 744 of thecorrelator 740 generates a code sequence, for example, a ZC sequenceused for the UE to generate 1-bit control information. To do so, thesequence generator 744 receives sequence information indicating asequence length and a sequence index from the controller 726. Thesequence information is known to both the Node B and the UE.

A conjugator 746 calculates the conjugate consequence of the ZCsequence. A multiplier 748 CDM-demultiplexes the control channel signalreceived from the DEMUX 724 by multiplying the control channel signal bythe conjugate sequence on an LB basis. An accumulator 750 accumulatesthe signal received from the multiplier 748 for the length of the ZCsequence. A channel compensator 752 channel-compensates the accumulatedsignal by the channel estimate received from the channel estimator 730.

In the derandomizer 742, an orthogonal code generator 754 generatesorthogonal codes by which the UE uses in transmitting the 1-bit controlinformation, according to orthogonal code information. A multiplier 758multiplies the channel-compensated signal by the chips of the orthogonalsequences on an LB basis. An accumulator 760 accumulates the signalreceived from the multiplier 758 for the number of LBs to which the1-bit control information was repeatedly mapped, thereby acquiring the1-bit control information. The orthogonal code information is signaledfrom the Node B to the UE so that both the Node B and the UE are awareof the orthogonal code information.

In a modified embodiment of the present invention, channel compensator752 is disposed between multiplier 758 and accumulator 760. Whilecorrelator 740 and derandomizer 742 are separately configured in FIG.7B, sequence generator 744 of correlator 740 and orthogonal codegenerator 754 of derandomizer 742 can be incorporated into a singledevice depending on a configuration method. For example, if correlator740 is configured so that sequence generator 744 generates a ZC sequencewith an orthogonal code applied on an LB basis for each UE, multiplier758 and orthogonal code generator 754 of derandomizer 742 are not used.Thus, a device equivalent to that illustrated in FIG. 7B is achieved.

A second embodiment of the present invention implements Method 2described in equation (3).

FIG. 8 is a diagram illustrating a transmission mechanism for controlinformation according to an embodiment of the present invention.

Referring to FIG. 8, one slot includes a total of 7 LBs, and the fourthLB carries a pilot signal in each slot. Hence, one subframe has 14 LBsin total, and 2 LBs are used for pilot transmission and 12 LBs forcontrol information transmission. While one RU is used for transmittingcontrol information herein, a plurality of RUs can be used to support aplurality of users.

The same 1-bit control information occurs 6 times in each slot, thus 12times in one subframe. For frequency diversity, frequency hopping isperformed for the control information on a slot basis. A random phase isapplied to a ZC sequence in each LB carrying the control information.The resulting randomization of the ZC sequence randomizes inter-cellinterference.

Random phase values applied to the ZC sequence in LBs are φ₁, φ₂, . . ., φ₁₂ 802 to 824. The ZC sequence is multiplied by e^(jφ) _(m) (m=1, 2,. . . , 12), thus being phase-rotated. As a random phase sequence beinga set of random phase values for LBs is cell-specific, the inter-cellinterference is randomized. That is, since the correlation betweenrandomized ZC sequences used for LBs of different cells is randomlyphase-rotated over one subframe, interference between control channelsfrom the cells is reduced.

The Node B signals the random phase sequence to the UE so that both areaware of the random phase sequence. To reduce the inter-cellinterference, a cell-specific random phase value can also be applied tothe pilot signal. The Node B signals the random phase value to the UE sothat both are aware of the random phase sequence.

FIG. 9 is a diagram illustrating another transmission mechanism forcontrol information according to an embodiment of the present invention.

Referring to FIG. 9, one slot includes a total of 6 LBs and 2 SBscarrying a pilot signal. Hence, one subframe has 12 LBs in total, and 4LBs are used for pilot transmission and 12 LBs for control informationtransmission. The same 1-bit control information occurs 6 times in eachslot, thus 12 times in one subframe. For frequency diversity, frequencyhopping is performed for the control information on a slot basis. Randomphase values applied to the ZC sequence in LBs are φ₁, φ₂, . . . , φ₁₂902 to 924.

FIGS. 10A and 10B are block diagrams illustrating a transmitter in theUE according to an embodiment of the present invention.

Referring to FIG. 10A, the transmitter includes a controller 1010, apilot generator 1012, a control channel signal generator 1014, a datagenerator 1016, a MUX 1017, an S/P converter 1018, an FFT processor1019, a mapper 1020, an IFFT 1022, a P/S converter 1024, a CP adder1030, and an antenna 1032. Components and an operation related to ULdata transmission will not be described herein.

The controller 1010 provides overall control to the operation of thetransmitter and generates control signals required for the MUX 1017, theFFT processor 1019, the mapper 1020, the pilot generator 1012, thecontrol channel signal generator 1014, and the data generator 1016. Acontrol signal provided to the pilot generator 1012 indicates a sequenceindex indicating an allocated pilot sequence and a time-domain cyclicshift value, for pilot generation. Control signals associated with ULcontrol information and data transmission are provided to the controlchannel signal generator 1014 and the data generator 1016.

The MUX 1017 multiplexes a pilot signal, a data signal, and a controlchannel signal received from the pilot generator 1012, the datagenerator 1016, and the control channel signal generator 1014 accordingto timing information indicated by a control signal received from thecontroller 1010, for transmission in an LB or an SB. The mapper 1020maps the multiplexed information to frequency resources according toLB/SB timing information and frequency allocation information receivedfrom the controller 1010.

When only control information is transmitted without data, the controlchannel signal generator 1014 generates a control channel signal byapplying a ZC sequence randomized on an LB basis to control informationin the afore-described method.

The S/P converter 1018 converts the multiplexed signal from the MUX 1017to parallel signals and provides them to the FFT processor 1019. Theinput/output size of the FFT processor 1019 varies according to acontrol signal received from the controller 1010. The mapper 1020 mapsFFT signals from the FFT processor 1019 to frequency resources. The IFFTprocessor 1022 converts the mapped frequency signals to time signals andthe P/S converter 1024 serializes the time signals. The CP adder 1030adds a CP to the serial signal and transmits the CP-added signal throughthe transmit antenna 1032.

FIG. 10B is a detailed block diagram illustrating the control channelsignal generator 1014 according to an embodiment of the presentinvention.

Referring to FIG. 10B, a sequence generator 1042 of the control channelsignal generator 1014 generates a code sequence, for example, a ZCsequence to be used for LBs. A randomizer 1044 generates a random phasevalue for each LB and multiplies the random phase value by the ZCsequence in each LB. To do so, the sequence generator 1042 receivessequence information such as a sequence length and a sequence index fromthe controller 1010 and the randomizer 1044 receives random sequenceinformation about the random phase value for each LB from the controller1010. Then, the randomizer 1044 rotates the phase of the ZC sequence bythe random phase value in each LB, thus randomizing the phase of the ZCsequence. The sequence information and the random sequence informationare known to both the Node B and the UE.

A control information generator 1040 generates a modulation symbolhaving 1-bit control information and a repeater 1043 repeats the controlsymbol to produce as many control symbols as the number of LBs allocatedto the control information. A multiplier 1046 CDM-multiplexes thecontrol symbols by multiplying the control symbols by the randomized ZCsequence on an LB basis, thus producing a control channel signal.

The multiplier 1046 functions to randomize the symbols output from therepeater 1043 by the randomized ZC sequence on a symbol basis. Amodified embodiment of the present invention can be contemplated byreplacing the multiplier 1046 with a device that performs a functionequivalent to applying or combining the randomized ZC sequence to orwith the control symbols. For example, multiplier 1046 can be replacedwith a phase rotator that changes the phases of the control symbolsaccording to the phase values of the randomized ZC sequence, φ_(m) orΔ_(m).

FIGS. 11A and 11B are block diagrams illustrating a receiver in the NodeB according to an embodiment of the present invention.

Referring to FIG. 11A, the receiver includes an antenna 1110, a CPremover 1112, an S/P converter 1114, an FFT processor 1116, a demapper1118, an IFFT processor 1120, a P/S converter 1122, a DEMUX 1124, acontroller 1126, a control channel signal receiver 1128, a channelestimator 1130, and a data demodulator and decoder 1132. Components andan operation associated with UL data reception will not be describedherein.

The controller 1126 provides overall control to the operation of thereceiver. It also generates control signals required for the DEMUX 1124,the IFFT processor 1120, the demapper 1118, the control channel signalreceiver 1128, the channel estimator 1130, and the data demodulator anddecoder 1132. Control signals related to UL control information and dataare provided to the control channel signal receiver 1128 and the datademodulator and decoder 1132. A control signal indicating a sequenceindex indicating a pilot sequence allocated to the UE and a time-domaincyclic shift value is provided to the channel estimator 1130. Thesequence index and the time-domain cyclic shift value are used for pilotreception.

The DEMUX 1124 demultiplexes a signal received from the P/S converter1122 into a control channel signal, a data signal, and a pilot signalaccording to timing information received from the controller 1126. Thedemapper 1118 extracts those signals from frequency resources accordingto LB/SB timing information and frequency allocation informationreceived from the controller 1126.

Upon receipt of a signal including control information from the UEthrough the antenna 1110, the CP remover 1112 removes a CP from thereceived signal. The S/P converter 1114 converts the CP-free signal toparallel signals and the FFT processor 1116 processes the parallelsignals by FFT. After processing in the demapper 1118, the FFT signalsare converted to time signals in the IFFT processor 1120. The P/Sconverter 1122 serializes the IFFT signals and the DEMUX 1124demultiplexes the serial signal into the control channel signal, thepilot signal, and the data signal.

The channel estimator 1130 acquires a channel estimate from the pilotsignal received from the DEMUX 1124. The control channel signal receiver1128 channel-compensates the control channel signal received from theDEMUX 1124 by the channel estimate and acquires the control informationtransmitted by the UE. The data demodulator and decoder 1132channel-compensates the data signal received from the DEMUX 1124 by thechannel estimate and then acquires data transmitted by the UE based onthe control information.

When only control information is transmitted without data on the UL, thecontrol channel signal receiver 1128 acquires the control information inthe manner described with reference to FIGS. 8 and 9.

FIG. 11B is a detailed block diagram illustrating the control channelsignal receiver 1128 according to an embodiment of the presentinvention.

Referring to FIG. 11B, the control channel signal receiver 1128 includesa correlator 1140 and a derandomizer 1142. A sequence generator 1144 ofthe correlator 1140 generates a code sequence, for example, a ZCsequence used for the UE to generate control information. To do so, thesequence generator 1144 receives sequence information indicating asequence length and a sequence index from the controller 1126. Thesequence information is known to both the Node B and the UE.

A conjugator 1146 calculates the conjugate consequence of the ZCsequence. A multiplier 1148 CDM-demultiplexes the control channel signalreceived from the DEMUX 1124 by multiplying the control channel signalby the conjugate sequence on an LB basis. An accumulator 1150accumulates the product signal for the length of the ZC sequence. Themultiplier 1148 of the correlator 1140 can be replaced with a phaserotator that changes the phases of the control channel signal on an LBbasis according to the phase values d_(k) of the sequence received fromsequence generator 1144. A channel compensator 1152 channel-compensatesthe accumulated signal by the channel estimate received from the channelestimator 1130.

In the derandomizer 1142, a random value generator 1156 calculates theconjugate phase values of random phase values that the UE uses intransmitting the control information, according to random sequenceinformation. A multiplier 1158 multiplies the channel-compensated signalby the conjugate phase values on an LB basis. Like The multiplier 1046of the transmitter, the multiplier 1158 of the derandomizer 1142 can bereplaced with a phase rotator that changes the phases of the controlchannel signal on an LB basis according to the phase values φ_(m) orΔ_(m) of the random sequence received from the sequence generator 1156.

An accumulator 1160 accumulates the signal received from the multiplier1158 for the number of LBs to which the 1-bit control information wasrepeatedly mapped, thereby acquiring the 1-bit control information. Therandom sequence information is signaled from the Node B to the UE sothat both are aware of the random sequence information.

In a modified embodiment of the present invention, the channelcompensator 1152 is disposed between the multiplier 1158 and theaccumulator 1160. While the correlator 1140 and the derandomizer 1142are separately configured in FIG. 11B, the sequence generator 1144 ofthe correlator 1140 and the random value generator 1156 of thederandomizer 1142 can be incorporated into a single device depending ona configuration method. For example, if the correlator 1140 isconfigured so that the sequence generator 1144 generates a ZC sequenceto which a random sequence is applied for each UE, the multiplier 1158and the random value generator 1156 of the derandomizer 1142 are notused. Thus, a device equivalent to that illustrated in FIG. 11B isachieved. In this case, like the multiplier 1046 of the transmitter, themultiplier 1148 of the correlator 1140 can be replaced with a phaserotator that changes the phases of the control channel signal on asymbol basis according to the phase values (d_(k)+φ_(m)) or(d_(k)+Δ_(m)) of the sequence received from the sequence generator 1144.

The inter-cell interference randomization can be further increased bysetting a different phase value for each LB to each UE. The Node Bsignals the phase value of each LB to each UE.

Aside from a random sequence as a phase sequence applied to 12 LBscarrying 1-bit control information, an orthogonal phase sequence such asa Fourier sequence can be used in the second exemplary embodiment of thepresent invention. A Fourier sequence of length N is defined as

$\begin{matrix}{{{f_{k}(n)} = {\mathbb{e}}^{{- j}\frac{2\pi\;{kn}}{N}}},\left( {{n = 0},\ldots\mspace{11mu},{N - 1},{k = 0},\ldots\mspace{11mu},{N - 1}} \right)} & (5)\end{matrix}$

In equation (5), a different cell-specific value k is set for each cell.When phase rotation is performed on an LB basis using a differentFourier sequence for each cell, there is no interference among cells iftiming is synchronized among the cells.

The first and second exemplary embodiments can be implemented incombination. In the transmission mechanism of FIG. 5, LBs carrying 1-bitcontrol information are multiplied by an orthogonal code and then by arandom phase sequence. As the random phase sequence is cell-specific,the inter-cell interference is reduced.

A third embodiment of the present invention implements Method 3described in equation (4).

The time-domain cyclic shift value of a ZC sequence is cell-specific andchanges in each LB that carries control information, thereby randomizinginter-cell interference. To be more specific, a cell-specific cyclicshift value Δ_(m) applied to each LB is further applied in the timedomain in addition to a cyclic shift value d_(k) applied to each ofcontrol channels that are CDM-multiplexed in the same frequencyresources within a cell. The Node B signals the cell-specific cyclicshift value to the UE. The cell-specific cyclic shift value is set to belarger than the maximum delay of a radio transmission path in order tokeep the orthogonality of the ZC sequence.

To reduce the inter-cell interference, a cell-specific randomtime-domain cyclic shift value can also be applied to the pilot signal.The Node B signals the random time-domain cyclic shift value to the UEso that the random time-domain cyclic shift sequence is known to boththe Node B and the UE.

FIG. 12A is a diagram illustrating a transmission mechanism for controlinformation according to an embodiment of the present invention.

Referring to FIG. 12A, one slot includes a total of 7 LBs and the fourthLB carries a pilot signal in each slot. Hence, one subframe has 14 LBsin total, and 2 LBs are used for pilot transmission and 12 LBs forcontrol information transmission. While one RU is used for transmittingcontrol information herein, a plurality of RUs can be used to support aplurality of users.

Random time-domain cyclic shift values applied to the 12 LBs of the ZCsequence are Δ₁, Δ₂, . . . , Δ₁₂ 1202 to 1224. The ZC sequence iscyclically shifted by the random time-domain cyclic shift values 1202 to1224 on an LB basis to randomize the control information.

FIG. 12B is a detailed view of FIG. 12A. To CDM-multiplex differentcontrol channels within a cell, the same time-domain cyclic shift valued_(k) (k is a control channel index) applies to each LB, and torandomize interference between control information from adjacent cells,different cell-specific time-domain cyclic shift values 1202 to 1224apply to LBs. That is, the ZC sequence is additionally cyclicallyshifted by a time-domain cyclic shift value for each UE in the cell.Reference numerals 1230 and 1232 denote first and second slots,respectively in one subframe. For convenience sake, frequency hopping isnot shown.

When a UE-specific time-domain cyclic shift is used for additionalrandomization, the time-domain cyclic shift values 1202 to 1224 indicatea UE-specific random sequence and the combination of d_(k) and thetime-domain cyclic shift values 1202 to 1224 maintains orthogonalityamong the control channels within the same cell.

FIG. 13 is a diagram illustrating another transmission mechanism forcontrol information according an embodiment of the present invention.Time-domain cyclic shift values of a ZC sequence for 12 LBs are Δ₁, Δ₂,. . . , Δ₁₂ 1302 and 1324. The ZC sequence is cyclically shifted in eachLB by a time-domain cyclic shift value in order to randomize controlinformation.

A transmitter and a receiver according to the third exemplary embodimentof the present invention are identical in configuration to thoseillustrated in FIGS. 10A and 10B and FIGS. 11A and 11B, except that therandomizer 1044 illustrated in FIG. 10B randomizes a ZC sequence withrandom time-domain cyclic shifts on an LB basis, and the random valuegenerator 1156 illustrated in FIG. 11B calculates the conjugate phasevalue of the random time-domain cyclic shift value of each LB andprovides it to the multiplier 1158.

The first and third embodiments can be implemented in combination. Thatis, in the transmission mechanism of FIG. 5, control information ismultiplied by an orthogonal code, and then additionally by a randomcyclic shift sequence on an LB basis as illustrated in FIG. 12 or FIG.13. As the random cyclic shift sequence is different for each cell, theinter-cell interference is reduced.

As is apparent from the above description, the present inventionadvantageously reduces inter-cell interference by applying a randomphase or a cyclic shift value to each block on a cell basis or on a UEbasis, when UL control information from different users is multiplexedin a future-generation multi-cell mobile communication system.

While the invention has been shown and described with reference tocertain preferred embodiments thereof, they are mere preferredapplications. For example, the embodiments of the present invention areapplicable to control information with a plurality of bits, such as aCQI, as well as 1-bit control information. Also, a random value for acode sequence used for control information can be applied in apredetermined resource block basis as well as on an LB basis. Thus, itwill be understood by those skilled in the art that various changes inform and details may be made therein without departing from the spiritand scope of the present invention as defined by the appended claims.

1. A method for transmitting control information by a transmitter in aSingle Carrier-Frequency Division Multiple Access (SC-FDMA) system,comprising the steps of: generating different orthogonal codes fordifferent slots, each comprising a plurality of SC-FDMA symbols in asubframe; generating, by the transmitter, a control channel signal bymultiplying control symbols carrying control information by a sequence;and multiplying the control channel signal by chips of the orthogonalcodes on an SC-FDMA symbol basis, and transmitting the multipliedcontrol channel signal in the SC-FDMA symbols.
 2. The method of claim 1,wherein a combination of the orthogonal codes used in the subframe isdifferent for each cell.
 3. The method of claim 1, wherein a combinationof the orthogonal codes used in the subframe is different for at leastone of each cell and each User Equipment (UE).
 4. The method of claim 1,wherein the sequence is a cell-specific Zadoff-Chu (ZC) sequence.
 5. Themethod of claim 1, wherein the multiplication and transmission comprisesmultiplying as many control symbols carrying the control information asthe number of the SC-FDMA symbols by the randomized sequences andtransmitting the multiplied control symbols.
 6. A method for receivingcontrol information by a receiver in a Single Carrier-Frequency DivisionMultiple Access (SC-FDMA) system, comprising the steps of: generatingdifferent orthogonal codes for different slots each comprising aplurality of SC-FDMA symbols in a subframe; multiplying by the receiver,a received control channel signal by a conjugate sequence of a sequence;and acquiring the control information by multiplying the multipliedcontrol channel signal by chips of the orthogonal codes on an SC-FDMAsymbol basis.
 7. The method of claim 6, wherein a combination of theorthogonal codes used in the subframe is different for each cell.
 8. Themethod of claim 6, wherein a combination of the orthogonal codes used inthe subframe is different for at least one of each cell and each UserEquipment (UE).
 9. The method of claim 6, wherein the sequence is acell-specific Zadoff-Chu (ZC) sequence.
 10. The method of claim 6,wherein the acquisition comprises multiplying as many control symbolsforming the control channel signal as the number of the SC-FDMA symbolsby the conjugate sequence.
 11. An apparatus for transmitting controlinformation in a Single Carrier-Frequency Division Multiple Access(SC-FDMA) system, comprising: a control channel signal generator forgenerating a control channel signal by multiplying control symbolscomprising control information by a sequence; and a transmitter forgenerating different orthogonal codes for different slots eachcomprising a plurality of SC-FDMA symbols in a subframe, multiplying thecontrol channel signal by chips of the orthogonal codes on an SC-FDMAsymbol basis, and transmitting the multiplied control channel signal inthe SC-FDMA symbols.
 12. The apparatus of claim 11, wherein acombination of the orthogonal codes used in the subframe is differentfor each cell.
 13. The apparatus of claim 11, wherein a combination ofthe orthogonal codes used in the subframe is different for at least oneof each cell and each User Equipment (UE).
 14. The apparatus of claim11, wherein the sequence is a cell-specific Zadoff-Chu (ZC) sequence.15. The apparatus of claim 11, wherein the randomizer multiplies as manycontrol symbols comprising the control information as the number of theSC-FDMA symbols by the randomized sequences and transmitting themultiplied control symbols.
 16. An apparatus for receiving controlinformation in a Single Carrier-Frequency Division Multiple Access(SC-FDMA) system, comprising: a receiver for receiving a control channelsignal comprising control information; and a control channel signalreceiver for multiplying the control channel signal by a conjugatesequence of a sequence and acquiring the control information bymultiplying the multiplied control channel signal by chips of differentorthogonal codes used for different slots each comprising a plurality ofSC-FDMA symbols in a subframe, on an SC-FDMA symbol basis.
 17. Theapparatus of claim 16, wherein a combination of the orthogonal codesused in the subframe is different for each cell.
 18. The apparatus ofclaim 16, wherein a combination of the orthogonal codes used in thesubframe is different for at least one of each cell and each UserEquipment (UE).
 19. The apparatus of claim 16, wherein the sequence is acell-specific Zadoff-Chu (ZC) sequence.
 20. The apparatus of claim 16,wherein the control channel signal receiver multiplies as many controlsymbols forming the control channel signal as the number of the SC-FDMAsymbols by the orthogonal codes.